The XSetDeviceButtonMapping request sets
the mapping of the specified device. If it succeeds, the X server generates
a DeviceMappingNotify event, and XSetDeviceButtonMapping returns MappingSuccess.
Element map[i] defines the logical button number for the physical button
i+1. The length of the list must be the same as XGetDeviceButtonMapping
would return, or a BadValue error results. A zero element disables a button,
and elements are not restricted in value by the number of physical buttons.
However, no two elements can have the same nonzero value, or a BadValue
error results. If any of the buttons to be altered are logically in the
down state, XSetDeviceButtonMapping returns MappingBusy, and the mapping
is not changed.

The XGetDeviceButtonMapping request returns the current
mapping of the specified device. Buttons are numbered starting from one.
XGetDeviceButtonMapping returns the number of physical buttons actually
on the device. The nominal mapping for a device is map[i]=i+1. The nmap argument
specifies the length of the array where the device mapping is returned,
and only the first nmap elements are returned in map_return.

An invalid
device was specified. The specified device does not exist or has not been
opened by this client via XOpenInputDevice. This error may also occur if
the specified device is the X keyboard or X pointer device.

BadMatch

This
error may occur if an XGetDeviceButtonMapping or XSetDeviceButtonMapping
request was made specifying a device that has no buttons.

BadValue

Some
numeric value falls outside the range of values accepted by the request.
Unless a specific range is specified for an argument, the full range defined
by the argument's type is accepted. Any argument defined as a set of alternatives
can generate this error.